The present invention relates to a process for the production of flexible plates, which can be used for the production of prints in flexography, letterpress or dry-offset printing, and it also relates to a device for implementing the process.
More exactly, the invention relates to a process for treating photopolymer sheets of any size very rapidly so as to convert them into printing plates.
It is already known that a plate for flexography or letterpress printing may be obtained by exposing a sheet of photopolymer sensitive material to ultraviolet radiation, with the interposition of a negative film which leaves the areas which are to come into relief on the finished plate exposed to the radiation.
The radiation cures these areas and the material of the protected surface is subsequently removed by brushing it with the aid of flat or rotary brushes or by spray nozzles; with a solvent or water acting as wetting agent. The operation is continued until the areas which have been exposed are sufficiently in relief.
A first object of the invention is to automate the entire etching process completely.
Moreover, a large range of photopolymer sheets of all thicknesses and in all sizes (up to 50.times.80 inches) currently exist on the market Semi-automatic machines are already manufactured on which the photopolymer plate is fixed or stuck to the plate-holding tray and a flat brush with orbital movement, steeped in an etching bath, makes it possible to make plates.
Another object of the invention is therefore to make photopolymer plates of all sizes and thicknesses, in a simple machine, making it possible to insert an already exposed plate from one side and to recover it after etching, almost dry, in as short a time as possible.
In order to achieve these objects, several problems had to be solved, in particular:
--reducing the duration of the etching operation; PA1 --automatic holding of the plate in the etching position; PA1 --putting the plate in the etching position automatically; PA1 --uniform etching over the entire surface; PA1 --etching sheets of any thickness without special adjustments to be performed; PA1 --etching sheets of any size. PA1 --insertion of the sheet sensitive side facing upwards, at high speed, on an etching plane and beneath a set of brushes; PA1 --etching by the resultant of an alternating movement of the flat brushes and of a to-and-fro movement of the set of brushes in a horizontal direction perpendicular to that of the brushes, the sheet being held automatically during etching. PA1 --rapid introduction and attachment of the sheet sensitive side upwards; PA1 --putting the sheet in position beneath the brushes and lowering the brushes. PA1 --automatic raising of the brushes; PA1 --transfer of the sheet towards the unit for automatically rinsing and cleaning both sides; PA1 --transfer into the pre-drying part.